Data storage systems



y 1970 JEAN-PAUL ARCHAMBAULT'ETAL 3,512,973

DATA STORAGE SYSTEMS Filed Dec. 16, 1965 JEAN PAUL ARCHAMBAULT JOHN RICHARD MANHARDT l NVENTORS W :1 W

ATTORNEY United States Patent 3,512,973 DATA STORAGE SYSTEMS llean-Paul Archambault and John Richard Manhardt, Nashua, NH, assignors to Itek Corporation, Lexington,

Mass., a corporation of Delaware Filed Dec. 16, 1965, Ser. No. 514,176

Int. Cl. G03c 5/24, 5/30 U.S. Cl. 96-48 g 19 Claims ABSTRACT OF THE DISCLOSURE A process for recording information comprising exposing image-wise a photosensitive copy medium, contacting the medium with a developer comprising a solution of metal ions which are at least as strong oxidizing agents as ionic copper, and then contacting the copy medium with a reducing agent for the metal ions and wherein at least the solution of metal ions or the reducing agent solution contains a sulfur containing nonionic surfactant such as a thioether surfactant. The invention also relates to the improved developer system used in the above process.

This invention relates to data storage systems. More precisely, the invention disclosed herein relates to data storage systems which include metal containing developer systems for retrieval of data stored in the media of the systems.

A principal object of the present invention is to provide an improved data storage system.

Another object of the present invention is to provide an improved data storage systemwhich includes a developer system of improved stability.

Still another object of the present invention is to provide an improved data storage system in which data is stored in media comprising photoconductive materials and retrieved therefrom by a developer system of improved stability.

Other objects and advantages of the present invention will in part appear hereinafter or will in part be apparent to those well skilled in the art.

The advantages which flow from the practice of our invention are especially apparent when the image storage system comprises media in which a photoconductor is a photosensitive component thereof. Said systems are described in more detail in commonly owned U.S. patent application Ser. No. 199,211, filed May 14, 1962, by E. Berman et a1., now abandoned. In accordance with the invention disclosed in the aforesaid application, media comprising radiation sensitive photoconductive materials such as zinc oxide, titanium dioxide, zinc sulfide, cadmium sulfide, indium oxide and the like are briefly exposed to a source of radiant energy. Such exposure establishes reversible image patterns in the media. The image patterns can be retrieved by contacting at least the exposed portion of the media with a chemical redox system capable of reacting on contact with the exposed portions to deposit thereon, species of the redox system which can be interpreted either directly or subsequently by visual readout.

Commonly owned copending U.S. patent application, Ser. No. 360,112, filed Apr. 15, 1964, by E. Berman et a1. discloses developer systems which are especially useful in retrieving quality image patterns from media comprising photoconductor materials. In accordance with the teachings of said application, the retrieval involves a two-step process. In the first step, exposed photoconductor containing media are contacted with a redox system comprising a chemical compound capable of reacting on contact with the exposed portions of said media to estab- "ice lish thereon a latent irreversible image pattern. Suitable redox systems include solutions comprising ions of such metals as silver, gold, mercury, copper and platinum. The latent irreversible image pattern is next contacted with an amplifying solution which comprises an acid and a reducing agent capable of reducing the compound applied to the media in the first step. Thereafter, the media is fixed in conventional fashions.

An outstanding problem in the use of developer systems described above arises when said systems are employed to successively retrieve image patterns from a plurality of photoconductor containing media. In continuous processes, for example, the amplifying solution becomes progressively contaminated by the compound of the solution applied to the media separately in the first step. This contamination manifests itself in the form of phenomena known to the art as mirroring and sludging which are merely different manners in which the precipitated reaction product of the compound and reducing agent are deposited from the amplifying solution. Accordingly, as mirroring and sludging progress, the effectiveness of the reducing agent in the amplifying solution is diminished in a direct fashion. Moreover, said mirroring or sludging adversely impairs the overall quality of images obtained in solutions comprising same. For example, the precipitated product is believed to hinder uniform development of image patterns since same can obstruct migration of the reducing agent to the surface of the media comprising the latent irreversible image pattern.

We have discovered that the stability of developer systems of the present invention can be improved in a surprisingly unexpected fashion by the use therein of a particular class of non-ionic surfactants. Broadly, the particular class of non-ionic surfactants which are useful in the practice of our invention are the non-ionic, sulfur containing surfactants known to the art generally as thioethers. Especially preferred non-ionic thioethers are the polyethylene glycol tertdodecyl thioethers. Others will be mentioned hereinafter.

The most preferred embodiment of our invention will be better understood by reference to-FIG. 1 which illustrates in schematic fashion an arrangement of apparatus suitable for practicing our invention.

Referring now to FIG. 1, image patterns can be stored in image storage medium of the present invention, 12, by exposure thereof to exposure means 14. Exposure means 14 include source 16 of activating radiation, transparency 18, comprising an information image pattern desired to be stored, and appropriate optical system 20, for focusing the image on medium 12. In general, image patterns can be stored in media of the present invention by exposure thereof to a source of radiation 16, having a wavelength such that the image storage media can absorb same. The best results are realized by exposing media of the present invention to light having a wavelength, between about 0.2 micron to about 0.5 micron. However, since media suitable in the practice of the present invention can oftentimes include sensitizers such as dyes which can alter the spectral response thereof, other sources can be used. Suitable light sources include mercury arc lamps, tungsten arc lamps, photoflash lamps and the like. The time of exposure will be determined primarily by such factors as the nature and strength of source 16 and the distance of the medium 12, from the source 16. Such factors are routine considerations normally encountered in conventional photographic processes. Thus, proper exposure time will be readily determined by one well skilled in the art. As an example, however, exposure times of considerably less than about 20 seconds and more often than not, less than about seconds are normally suitable.

After exposure, medium 12 is conveyed to tank 22. In the most preferred embodiment of our invention, tank 22 contains an aqueous or partially aqueous solution of a compound comprising silver, mercury, copper, gold or platinum, for example. The application of the solution of tank 22 to medium 12 converts the image pattern therein to an irreversible form. Said irreversible image pattern is usually latent but oftentimes can be visible or partially visible.

After applying the solution of tank 22 to medium 12, said medium can be washed, if desired. However, most conveniently, medium 12 is conveyed to bath 24. Bath 24 comprises an aqueous or partially aqueous solution of a reducing agent for the compound in tank 22 such asmethylaminophenol sulfate or other suitable organic and inorganic photographic reducing agents. Suitable reducing agents include hydroquinone or derivatives thereof, oand p-aminophenol, p-methylaminophenol sulphate (metal) p-hydroxyphenylglycine, oand p-phenylenediamine, l-phenyl-3-pyrazolidone and others which could be mentioned. Suitable inorganic photographic reducing agents such as those comprising ferrous, titanous and vanadous ions can also be employed. The concentration of said reducing agent can vary over a wide range. For example, the reducing agent can be present in amounts from 0.5 percent by weight of solution to 40 percent by weight.

Oftentimes alkali metal sulfitespreferably sodium sulfitecan be included in the solution of tank 24 to advantageously retard oxidation of the reducing agent. The preferred concentration of said sulfite is from about 0.5 percent by weight of solution to saturation concentrations of amounts somewhat higher.

In accordance with the preferred practice of the present invention, the solution of tank 24 comprises a nonionic surfactant. Broadly, the non-ionic surfactants suitable in the practice of the present invention include those which are known to the art as thioethers and conform to the following generic formula:

where R is an alkyl radical with those having less than about 6 carbon atoms being preferred, or a polyhydric alcohol radical preferably having less than about 8 carbon atoms or polyoxyethylene glycol radical; S is sulfur and R is an alkyl radical preferably having less than about 14 carbon atoms. Accordingly, suitable representative non-ionic thioethers include butyl dodecyl thioether, ethyl octyl thioether, propoyl heptyl thioether, methyl 3,4,5,6 tetrahydroxy hexyl thioether. Suitable concentrations of the non-ionic surfactant include those ranging from about 0.01 percent by weight of solution to about 3 percent by weight but amounts less than about 1.0 percent are most suitable. The solution of tank 24 can also contain an ionic surfactant, if desired.

Broadly, the ionic surfactants suitable in the practice of our invention include those surfactants or dispersants which achieve dispersion by reason of the fact that they carry a charge which can be anionic or cationic in nature. The most preferred ionic surfactants are those which are cationic in nature. The following is a listing of some of the ionic surfactants suitable in the practice of the present invention:

Salts of primary alkylamines, the hydrophobic alkylaryl radical of which possesses at least 8 carbon atoms or mixtures of these compounds;

Compounds comprising a basic hydrophilic, nitrogen containing group which is bonded via an amide bond with the hydrophobic group;

Compounds comprising a basic hydrophilic nitrogen containing group which forms part of the morpholine ring system;

Compounds comprising a basic hydrophilic, nitrogen containing group which forms part of a heterocyclic fivemembered ring;

Compounds comprising a basic, hydrophilic, nitrogen containing group which forms part of a pyridine ring system;

Salts of primary alkylamines, comprising a hydrophobic alkyl radical which possesses at least 8 carbon atoms, or mixtures of these compounds;

Compounds comprising a basic hydrophilic nitrogen containing group which is bonded through an ether group with the hydrophobic group;

Salts of sulphuric acid semi-esters of aliphatic alcohols;

Alkylaryl sulphonates.

Suitable concentrations of the aforesaid surfactants range from 0.01 percent byweight of solution to about 3 percent by weight with amounts less than about 1 percent being most suitable.

Medium 12 is generally permitted to remain in contact with the solution of tank 24 for about 2 or 3 seconds but shorter or longer times can be suitably employed. After immersion in tank 24, additional processing steps can be applied to medium 12 such as Washing, fixing and the like.

Although we prefer to include the non-ionic surfactant in the amplifying solution, e.g. tank 24 of FIG. 1, nevertheless, said surfactant can be included in tank 22 of FIG. 1, if desired, or in both tanks.

Details of manners of practicing our invention are set forth in the following example. It is to be understood that the example is illustrative in nature and in no way to be construed so as to limit our invention beyond those limitations expressly set forth in the present specification or in the claims which appear hereinafter.

EXAMPLE 1 A three station, continuous photographic processor embodying the features of FIG. 1 was used to expose and develop media comprising titanium dioxide as the radiation sensitive component thereof. Said media were prepared by continually coating a roll of single weight baryta paper with a dispersion comprising about 1 part by weight of acrylic resin to about 4 parts by weight of finely divided titanium dioxide. The media were processed through the machine at a rate of about 10 feet per minute. The media were first exposed through a transparency in the exposure station and then conveyed through two stations in which liquids were applied to the media. The first liquid application station comprised a solution which contained about 34 grams AgNO in 1000 mls. of water. Thereafter, the media were conveyed through a second liquid application station which comprised about 8.4 grams metol, about 1.4 grams of Nonic 218, a tertdodecyl thioether sold by Pennsalt Chemical Company, and 1000 mls. of water. The solutions in each of the liquid application stations were continually replenished throughout the run. After treatment in each of the stations, the media were fixed in a conventional fashion. After 8 hours of continuous running, no mirroring and no substantial sludging is detected in either solution. At the conclusion of the run, the solutions in each station can be conveniently removed therefrom simply by flushing and washing the station with water.

However, when the Nonic 218 is omitted from either of the abovementioned stations, sludging and mirroring occurs in about 15 minutes in the station comprising the solution of metol. After about 45 minutes the run is stopped but before replacing the solution of metol, cleaning of the station with abrasive or chemical cleaners is required in order to remove precipitated products therefrom.

The above example illustrates the eificacy of the nonionic surfactants of the present invention in advantageously stabilizing the development system. Substantially the same results can be obtained when other thioethers heretofore mentioned are involved or other of the aforementioned metal compounds are used in place of the silver nitrate or when other reducing agents for said compounds are utilized. Also, it is to be understood that other ingredients such as ionic surfactants, sodium sulfite, organic acids and the like can also be advantageously included in one or both of the liquid application stations. For example, we prefer to include a primary dodecyl amine acetate in the station comprising the reducing agent.

Many modifications of the details of the above example offered for the purposes of illustrating our invention can be introduced thereto without departing from the spirit and scope of the invention defined in the appended claims.

Having described our invention together with preferred embodiments thereof, as well as manners of practicing same, what we declare as new and desire to secure by U.S. Letters Patent is as follows:

1. In the process for producing an image which comprises the steps of:

(a) exposing a photosensitive copy medium comprising a photoconductor to thereby activate the copy medium in the exposed portions of the medium;

(b) contacting the medium with a solution of image forming materials comprising ions of metallic compounds which can be reduced as easily as copper; and

(c) contacting the medium with a second solution comprising a reducing agent for the ions of metallic compounds of the first solution, the improvement wherein at least one of said solutions comprises a non-ionic surfactant conforming to the following generic formula:

where R is chosen from the group consisting of alkyl radicals, radicals of polyhydric alcohols and polyethylene glycol radicals, S is sulfur and R is an alkyl radical.

2. The process of claim 1 wherein said non-ionic surfactant is a polyethylene glycol tertdodecyl thioether.

3. The process of claim 1 wherein said non-ionic dispersing agent is present in said second solution.

4. The process of claim 1 wherein at least one of said solutions contains an ionic surfactant.

5. The process of claim 1 wherein said solution of ions of metallic compounds comprises silver ions.

6. The process of claim 1 wherein said solution of ions of metallic compounds comprises copper ions.

7. The process of claim 1 wherein said solution of ions of metallic compounds comprises at least one member of the group consisting of silver ions, copper ions, gold ions, platinum ions, and mercury ions.

8. The process of claim 1 wherein said solution of ions of metallic compounds comprises silver nitrate.

9. In a process for recording information comprising exposing a photosensitive copy medium comprising a photoconductor, contacting the medium with a solution of ions of metallic compounds which can be reduced as easily as copper, and contacting the medium with a solution comprising a reducing agent for the ions of metallic compounds, the improvement wherein at least one of the solutions comprises a non-ionic thioether surfactant.

10. A developer composition comprising a solution which comprises a reducing agent for ions of metallic compounds which can be as easily reduced as copper and a non-ionic surfactant conforming to the following generic formula:

where R is chosen from the group consisting of alkyl radicals, radicals of polyhydric alcohols and polyethylene glycol radicals; S is sulfur and R is an alkyl radical.

11. The composition of claim 10 wherein said nonionic surfactant is a. polyethylene glycol tertdodecyl thioether.

12. The composition of claim 10 wherein said nonionic surfactant is a tertdodecyl thioether.

13. The composition of claim 10 wherein said solution contains an ionic surfactant.

14. The composition of claim 10 wherein said solution comprises a photographic reducing agent for silver ions.

15. In a developer composition comprising a solution which comprises a reducing agent for ions of metallic compounds which can be as easily reduced as copper, the improvement comprising adding to this solution a nonionic thioether containing surfactant.

16. A developer composition as in claim 10 wherein R is an alkyl radical having less than about 6 carbon atoms or a polyhydric alcohol radical having less than about 8 carbon atoms and R is alkyl radical having less than about 14 carbon atoms.

17. A developer composition comprising a solution which comprises ions of metallic compounds which can :be reduced as easily as copper and a non-ionic surfactant conforming to the following formula:

References Cited UNITED STATES PATENTS 3,152,903 10/1964 Shepard et al 96-64 3,252,798 5/ 1966 Jonker et al.

FOREIGN PATENTS 1,374,547 8/1964 France.

OTHER REFERENCES Technical Information on Dimethyl Sulphide, Crown Zellerbach Corp., Camas, Wash, 1961, p. 9.

NORMAN G. TORCHIN, Primary Examiner M. F. KELLEY, Assistant Examiner U.S. Cl. X.R. 9666 

